The present invention relates to flexible multilayer cables and, in particular, to a device and a method for directing the bending of such cables.
A major difficulty in the fabrication and use of multilayer flexible cables is the ability to bend them without subjecting the layers to damaging stresses. When such a cable is bent, the outer layer lengthens and the inner layer shortens, so that the inner layer buckles and/or the outer layer is placed in tension. These stresses on the layers increase as the bending angle increses from a flat to an angle of 90.degree. or more.
One method of avoiding such stress is to fabricate the cable with layers of unequal lengths. This method increses both the time and effort and, therefore, the cost, of manufacture, and usually limits the use of such a constructed cable to a particular use. Other solutions include the use of a loose bonding between the layers, for example by stitching, so that one layer may move lengthwise with respect to the other. This solution has some inherent problems, such as the need for lateral alignment between conductors in respective layers. Where such movement between layers is not permissible or possible, e.g., for layers which are bonded together, the stitching solution is not available.